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Full text of "High-speed civil transport study. Summary"



|MASA Contractor Rep^^^4234 



high-speed Civil Transport Study 

# 

Nummary 



poeing Commercial Airplanes 
f»Jew Airplane Development 



fONTRACT NASl-18377 
IepTEMBER 1989 



1 



{NASA-CR-42 JU) hii^H-^PEi-D CIVIL T H AN li t'O Ki 
STUDY. SUMMARY Fiuril Kcport (boeitiq 
CotniBcrcial Airplane Co,) H^ p 



Nrt9-276a7 



Onclas 
HI/05 022U515 



NASA Contractor Report 4234 



High-Speed Civil Transport Study 



Summary 



Boeing Commercial Airplanes 
New Airplane Development 
Seattle, Washington 



Prepared for 

Langley Research Center 

under Contract NASl-18377 



rUASA 

National Aeronautics and 
Space Administration 

Office of Management 

Scientific and Technical 
Information Division 

1989 



CONTENTS 

Page 

FIGURES AND TABLES v 

FOREWORD vii 

SUMMARY ix 

INTRODUCTION 1 

MARKET/MISSION REQUIREMENTS 3 

Market Needs Projections 3 

Required Vehicle Characteristics 5 

Air Transportation System 6 

Design Requirements 9 

ENVIRONMENTAL CONCERNS 10 

VEHICLE DEVELOPMENT 10 

Initial Assessment 10 

Final Assessment 14 

REQUIRED TECHNOLOGIES 17 

Advanced Jet Noise Reduction Concepts 17 

Emission Reduction Concepts 17 

Fuel Technology 19 

Aerodynamics 19 

Stability and Control 20 

Structures and Materials 20 

Weight and Balance -22 

Impact of Improved Technology 22 

ENVIRONMENTAL EVALUATION 23 

Upper-Atmosphere Emissions/Ozone Impact 23 

Community Noise 24 

Sonic Boom 26 

ECONOMIC EVALUATION 28 

Economic Viability 28 

CONCLUSIONS 30 

Market and Competition 30 

Environmental Concerns 30 

Technical Feasibility 31 

Economic Viability 31 



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ui 



Page 
RECOMMENDATIONS 31 

Technology Development Program 31 

Technology Needs 32 

REFERENCES 33 



IV 



FIGURES AND TABLES 

Figures Page 

1 High-Speed Civil Transport Activities 1 

2 High-Speed Civil Transport Study Plan and Schedule 2 

3 Year 2000 International Traffic Distribution Forecast Based on 

Total of 1,100,000 Passengers/Day 4 

4 Revenue Passenger Mile Forecast 4 

5 HSCT Traffic Distribution-Year 2000 5 

6 Overwater Distance 6 

7 Fleet Size Versus Seats 7 

8 Effect of Design Range on Fleet Size 7 

9 Fleet Size Versus Turn/Through Time 8 

10 Superhub Airport Network 9 

11 Units Required-Year 2015 9 

12 Average Trip Time— Superhub System 10 

13 Conventional-Fueled Engine Concepts 12 

14 Cryogenically Fueled Engine Concepts 13 

15 Mach 2.4 Configuration 14 

16 Mach 3.2 Configuration 14 

17 Mach 3.8 Configuration 15 

18 Mach 4.5 Configuration 15 

19 Mach 6.0 Configuration 16 

20 Mach 10.0 Configuration 16 

21 Mach 2.4 Baseline Configuration 17 

22 Jet Noise Reduction Concepts 18 

23 Drag Breakdown— Mach 2.4 Baseline 19 

24 Lift/Drag Versus Mach— Mach 2.4 Baseline 20 

25 Structural Material Candidates and Projected Temperature 

Range for HSCT Application 21 

26 Impact of Technology— Mach 2.4 Baseline 22 

27 Impact of Technology— Mach 2.4, 247-Seat Airplane With 

Year 2000 Certification, 5,000-nmi Design Range 23 

28 HSCT Growth Strategy 24 

29 Noise Contour at 85 dBA-Comparison of HSCT to 747-200 25 

30 Low-Sonic-Boom Configuration 26 

31 Mach 1.5 Pressure Signature and Loudness Predictions 27 

32 Economic Viability— Technology Impact on Fleet Size Based on 

Mach 2.4, 247-Seat Design With 5,000-nmi Range 29 

33 Economic Viability— Impact of Speed Based on 247-Seat Design 

With 5,000-nmi Range 29 

Tables 

1 High-Speed Civil Transport Mission Perspective 3 

2 Design Mach Number Selections 11 



FOREWORD 



This report documents work completed for phases I, II, and III on high-speed civil transports under 
NASA contract NASl-18377. The New Airplane Development group of Boeing Commercial Air- 
planes, Seattle, Washington, was responsible for the study. Charles E. K. Morris, Jr., NASA Langley 
Research Center, was NASA program manager. Michael L. Henderson and Frank H. Brame were pro- 
gram managers for Boeing Commercial Airplanes. Boeing task managers were: Robert M. Kulfan for 
phase I and II Engineering; John D. Vachal for phase III Engineering; William H. Lee and Roger W. 
Roll for Marketing; and Donald W. Hayward and Edward N. Coates for Special Factors. 

The Boeing team consisted of— 



Manager HSCT Design Development 
Aerodynamics 



Configurations 

Finance 

Marketing 

Noise 

Payloads 

Propulsion 

Special Factors 

Structures and Materials 

Systems 
Weights 



M. I. K. MacKinnon 

D. N. Ball, T H. Hallstaff, G. T Haglund, 
J. C. Klein, S. S. Ogg, J. A. Paulson, 
S. E. Stark, P E Sweetland, T E. Trimbath, 
G. H. Wyatt 

T Derbyshire, V. K. Stuhr 

G. J. Gracey 

R. E. Bateman, T. Higman, S. C. Henderson 

J. G. Brown, G. L. Nihart 

D. P Lefebvre 

J. J. Brown, G. B. Evelyn, R. B. McCormick, 
J. Merrick, P. Ormiston 

N. M. Barr, J. H. Foster, O. J. Hadaller, 
A. M. Momenthy 

J. W. Fogelman, D. L. Grande, T. E. Munns, 
D. G. Stensrud, R. T Wagner 

A. W. Waterman, T. Timar 

J. D. Brown, M. W. Peak, J. P Rams 



PRECEDING PAGE BLANK NOT FILMED 



m^JL^-''"'-'-*"-'"^'-' ''^^ 



Vll 



SUMMARY 

A systems study of the potential for a high-speed commercial transport has addressed technology, 
economics, and environmental constraints. Market projections indicated a need for fleets of transports 
with supersonic or greater cruise speeds by the years 2000 to 2005. The associated design requirements 
called for a vehicle to carry 250 to 300 passengers over a range of 5,000 to 6,500 nautical miles. The 
study was initially unconstrained in terms of vehicle characteristics, such as cruise speed, propulsion 
systems, fuels, or structural materials. Analyses led to a focus on the most promising vehicle concepts. 
These were concepts that used a kerosene-type fuel and cruised at Mach numbers between 2.0 to 3.2. 
Further systems study identified the impact of environmental constraints (for community noise, sonic 
boom, and engine emissions) on economic attractiveness and technological needs. 

Results showed that current technology cannot produce a viable high-speed civil transport; signifi- 
cant advances are required to reduce takeoff gross weight and allow for both economic attractiveness 
and environmental acceptability. Specific technological requirements have been identified to meet 
these needs. 



3RECED!f4G PAGt: BLA^'K HUT FILMED 



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INTRODUCTION 

Present projections predict that the worldwide demand for long-range air travel will double by the 
year 2000 and nearly double again by year 2015. This growth in the market will occur at the same time 
that increasing numbers of aircraft in the existing fleet will be retired due to age and noise rules. 

Manufacturers must make difficult and long-lasting decisions in the next 5 to 10 years concerning 
future products so that sufficient time is allowed for development. One option to consider is a new 
generation of commercial transports that cruise at speeds of Mach 2.0 or greater and can serve both 
the Atlantic and Pacific markets. 

Boeing Commercial Airplanes conducted a three-phase study of the potential for future high-speed 
civil transports (HSCT) under NASA contract NASI- 18377 between October 1986 and August 1988. 
The primary objectives were to identify the most promising concepts in high-speed transports and to 
guide the development of requisite technology that may not flow directly from the National Aero-Space 
Plane or other existing programs. To achieve this it was necessary to examine the environmental, opera- 
tional, and nonvehicle factors that will influence the vehicle configuration, supporting facilities and 
systems requirements, and overall program viability. Also, it was essential to identify and account for 
those market and economic factors that must be considered to provide a commercially acceptable 
high-speed transport system. 

The study examined the requirements of a future HSCT as affected by the environment, oper- 
ational concerns related to other HSCTs and subsonic aircraft, and the market demand for aircraft 
after the year 2000. Market assumptions were developed for an HSCT operating in this timeframe. 
The study evaluated both supersonic and hypersonic aircraft. Initially, aircraft were evaluated through 
Mach 10.0; the latter phases looked at supersonic only (under Mach 6.0) (fig. 1). Propulsion concepts 
were investigated in conjunction with the fuel technology required. A screening process was employed 
to determine the best Mach number range for further investigation of the environmental issues such 
as community noise, effect on the ozone layer, and sonic boom. The economic impact of the configura- 
tions investigated were compared throughout the study. Figure 2 illustrates the flow of the study proc- 
ess through the three phases. 



Mach 


Supersonic 


Hypersonic 


Mission 


Transport 


Transport 


Fuel 


Conventional 


Cryogenic 


Certification date 


2000 to 2005 


2015 to 2025 



NASA contract 
Phase I ^ 

Phase II <4i 

Phase III •4- 



Mach 2.4 to 10 



2.4 to 5 



2.4 to 3.2 



Figure 1. High-Speed Civil Transport Activities 



5-U90027R1-124 



Table 1. High-Speed Civil Transport Mission Perspective 



Transport type 


Concorde 


U.S. SST 


HSCT 


Year In service 


1971 


1975 


2000-2015 


Market 


North Atlantic 


North Atlantic 


Atlantic and Pacific 


Range (nml) 


3,500 


3,500 


5,000-6,500 


Payload (passengers) 


100 


200 


250-300 


TOGW (lb) 


400,000 


750,000 


750,000 


Community noise requirements 


None 


Stage II 


Stage III 


Revenue required 








(cents/revenue passenger miles) 


87 


60 


9-10 



5-U90027H1-125 



Table 1 indicates the level of challenge posed by this goal of an economically attractive, environmen- 
tally acceptable HSCT Passenger count must increase significantly from the Concorde to be economi- 
cal, and noise and emission levels must be greatly reduced. 

A capable HSCT like the one postulated in table 1 would compete well even with advanced subson- 
ics because of reduced flight times. It is important that U.S. manufacturers understand the potential 
of such an airplane as a product or a competitor. Ignoring the HSCT's potential, or delaying the timely 
development of technology that could make it a viable product could bring about the loss of a signifi- 
cant national opportunity to the competition from abroad. If successful, this competition would reduce 
the United States' traditionally high market share in the international marketplace for large, 
long-range commercial transports. Even worse, commitment to a program without an adequate tech- 
nological and environmental database could lead to an expensive failure. Both arguments lead to the 
conclusion that it is justified and highly desirable to continue research and development of key technol- 
ogies for an environmentally and economically sound HSCT. 

MARKET/MISSION REQUIREMENTS 



Market Needs Projection 

The market forecast is based on major market area passenger flows as defined in the "Boeing 1987 
Current Market Outlook" (ref. 1). The Market Outlook covers the time period from 1987 through the 
year 2000 and projects that world air travel will grow at an average rate of 5.3% per year. The market 
application for an HSCT is derived from the "international scheduled" portion of this forecast that 
represents 22.8% of the total world demand for the year 2000. 

Not all of this market is applicable for a long-range airplane, however. Figure 3 graphically depicts 
that portion of the international traffic allocated to the HSCT. All passenger demands less than 300 
passengers per day, less than 2,500 nmi in distance, and all intraregional demands were excluded. As 
a result only 28% of the international demands (or about 6.4% of the world passenger forecast) are 
considered HSCT study markets. 

The traffic forecast for 2015 was developed by assuming the individual markets are maturing, and 
therefore grow at 85% of their average rates from the years 1995 through 2000. This resulted in almost 
doubling the year 2000 demand, with the Pacific Rim area forecast increasing at a greater rate (53% 
of the revenue passenger miles in year 2000 and 60% in 2015) (fig. 4). The total HSCT passenger de- 
mand potential (without allowances for stimulation) is forecast to be 315,000 passengers per day by 
year 2000 and 600,000 per day by 2015. This is certainly adequate potential traffic to justify a commer- 
cially viable HSCT However, if significant ticket price increases are required for HSCT configura- 
tions, market elasticity could reduce the demand for an HSCT below acceptable levels. 



Legend: 
g HSCT 
study 
markets 



North America to 
Europe it 'b 



North America 
to Asia 5.4% 



Europe to 
Asia, 3.9% 



Pacific 
Rim, 4.1% 



Other, 4.1% 




Under 2,500 nml, 
26.5% 



Intrareglonal, 
45.9% 

Figure 3. Year 2000 International Traffic Distribution Forecast Based on Totalof 1, 100,000 Passengers! Day 

5-U90027R3-ia8 



1,250 



1,000 — 



750 — 



Revenue 
passenger 
miles, billions 
per year 



500 — 



250 



Year 2015 
1,107 billion RPM 



Year 2000 
572 billion RPM 




Other 



Pacific Rim 



Europe to Asia 
and Pacific 



North America to 
Asia and Paplfic 



North America to 
Europe 



Figure 4. Revenue Passenger l\Aile Forecast 



4-U«»27R2-127 



Required Vehicle Characteristics 

The development of HSCT market requirements demanded an assessment of not only the size and 
distribution of the market, but also of certain airplane characteristics. These characteristics include 
speed, design range, airplane through time and airport turnaround time, and passenger seat count 
within the market. Each characteristic was examined parametrically and then in more detail as re- 
quired. The parametrics considered two basic environments: (1) an "unconstrained" environment 
(that is. Great Circle routing and sonic boom allowed over land), and (2) a "constrained" environment 
that assumed no sonic boom over land and some rerouting to maximize time spent in supersonic 
cruise. In both cases, existing airport curfews were observed and all the passengers were served within 
a postulated universal airline system. 

Additionally, the market potential is subject to certain unknowns in terms of stimulated passenger 
demand due to shorter trip times and decreased demand due to ticket price increases over subsonic 
prices. Stimulation, as such, was not included in the basic study; however, the effect of ticket price 
was examined. 

Figure 5 shows the distribution of nonstop passenger trips and revenue passenger miles. About 
half the passengers and 40% of the revenue passenger miles would be satisfied by a 4,000-nmi design 
range. Ninety percent of the passengers, representing 84% of the revenue passenger miles, could be 
satisfied by a 6,000-nmi design range. 

A detailed analysis was conducted of 10 specific market areas in which airplane productivity and 
HSCT passenger trip time savings were used to evaluate design-range capabilities. Design range is 
important because it affects the number of intermediate stops required to serve the airline's network. 
Stopovers will reduce airplane productivity and increase travel time. 

As seen in figure 6, four of these ten markets have more than 85% of their routes over water and 
the others range from 50% to 80% over water. These same four markets represent approximately half 
of the passengers and 41% of the revenue passenger miles. The remaining "mostly overland" markets 



100 



75 



Cumulative 
F>ercentage 



50 



25 



1 




Nonstop 

passenger 

trips 



1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 

Great Circle distance, nml 

Figure 5. HSCT Traffic Distribution - Year 2000 



4-U90027-128 



100 



Percentage gQ 
over water 




Eastern Western Europe 

North North to South 

America America America 

to Europe to Asia 



Pacific 
Rim 



Eastem 
North 
America 
to Asia 



Westem 
North 
America 
to Europe 



Mid-North Mid-North 
America America 
to Europe to Asia 



Europe 
to Asia 
and the 
Pacific 



Othef 



Figure 6. Overwater Distance 



4-U90027-128 



cannot use an HSCT as effectively as the overwater markets if there is a constraint forbidding any 
overland supersonic flight. These markets, then, will require flying long distances subsonic over land 
and reflect the need, in many cases, to deviate from Great Circle routing to reduce overland flight dis- 
tances. This natural differentiation of markets (predominantly over water versus over land) provides 
a useful division to evaluate the HSCT design-range requirements relative to productivity (number 
of airplanes required) and passenger trip time. 

Figures 7 through 9 are indicative of the overall results for the best-case potential: unconstrained, 
supersonic, overland flight with Great Circle routing. These results indicate maximum gains in produc- 
tivity between Mach 2.0 and Mach 8.0. There are, also, trades between Mach number and the other 
parameters. A 7,000-nmi design range, Mach 3.0 vehicle, for example, has the same productivity poten- 
tial as a 4,500-nmi design range, Mach 10.0 vehicle (fig. 8). 

Air TVansportation System 

Twenty-seven conventional airports were selected as primary candidates for use by the HSCT. A 
vehicle designed for a sea-level takeoff field length of 12,000 ft will impose little additional require- 
ments to existing runways at these international airports. Airport modifications required for the fleet 
of subsonic vehicles anticipated for the years 2000 to 2015 would cover most of the needs of a super- 
sonic transport in the Mach range considered most viable. Some additional modifications to taxiways 
and loading areas may be required because of the vehicle's length (60 ft longer than a 747). 



Units 



800 



700 — 



600 - 



500 - 



400 — 



300 — 



200 — 



7,000-nml design range 
2-hr turn/through time 



100 




12 3 4 5 



7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 
Design Mach number 

Figure 7. Fleet Size Versus Seats 

4-U90027-130 



900 



Number of units 
required 



800 - 



700 - 



600 - 



500 - 



400 - 



300 - 



2-hr turn/through time 
283 seats 



200 




Design range 
4,500 nmi 



2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 

Design Mach number 

Figure 8. Effect of Design Range on Fleet Size 

4-U90027R1-131 



800 



700 



600 



Number 
of units 
required 



500 



400 



300 



200 



100 




• 7,000-nml design range 

• 283 seats 



<y 



Turn/through 
time 4 hr 

3 hr 



1 



1 



I I 



<> 



-0 



2 hr 



1 hr 



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 

Design Mach number 

Figure 9. Fleet Size Versus Turn/Through Time 

4-U90027-132 



Consideration also must be given to the influence of high-speed travel in heretofore uncontrolled 
airspace; however, no special Air Traffic Control electronic equipment will be required. The HSCT-era 
avionics systems will greatly enhance HSCT integration into Air Traffic Control environments. 

Special airports would probably be required to accommodate the needs and improve the produc- 
tivity of a hypersonic HSCT (airplanes with cruise Mach number of 6.0 or greater), which is expected 
to operate with weights greater than 1 million pounds. This higher speed vehicle will also require spe- 
cial fuel systems and will probably not meet community noise standards. 

To improve the productivity of a hypersonic HSCT, the average stage length must be long enough 
to provide a substantial period of time at cruise. 

A network of strategically located "superhubs," shown in figure 10, was developed to maximize 
the average stage length of the hypersonic HSCT. These hubs would be fed by subsonic airplanes, with 
service between the hubs by airplanes with cruise speeds of Mach 6.0 and greater. The productivity, 
measured by units required, and the average trip time for this superhub system were compared when 
serving the same market, with more direct routing and either an all-subsonic fleet (Mach 0.84 cruise) 
or an all-supersonic fleet (Mach 3.2 cruise, Mach 0.9 over land). 

Figure 11 compares the units required in the year 2015 for each case. The all-subsonic system (with 
525-seat airplanes) requires about 560 units, while the all-supersonic, Mach 3.2 system (with 283 seats, 
subsonic over land, and waypoint routing) requires 50 fewer units. The third bar in figure 11 shows 
that the system using superhubs requires more units (90 more than the subsonic and 110 more than 
the supersonic system), but 370 of these are subsonic (and less expensive) airplanes. 

Figure 12 compares the average trip time for the three systems. Both the all-supersonic and the 
hypersonic-subsonic superhub system show significant gains over the all-subsonic system. The super- 
hub system at Mach 6.0, however, shows no gain over a Mach 3.2 system and only a 1 hr improvement 
at Mach 15.0. This is because the feed portion of the trip and the passenger transfer at each end of 
the high-speed leg consumes almost 4 hr (even assuming an optimistic 30-min transfer time). 

In conclusion, the benefits, in terms of the travel time savings of a dedicated superhub network, 
are minimal. Productivity gains are offset by the requirement for a large number of subsonic feed 




Figure 10. Superhub Airport Network 



4-U90027-133 



1,000 



Units 



500 — 





All subsonic 
Mach 0.84, 
525 seats, 
6,660 nmi 






All supersonic 




Superhub, mixed 
subsonic and Mach 8.0, 
283 seats 




iviacn j.^, 
283 seats, 


\V Dedicated \V 
sV\ Mach 8.0 Xv 

\N\\\\\\\^ 






t 


I 




5,500 nmi 






K 




Feed 
Mach 0.84 



Figure 1 1. Units Required- Year 2015 



4-U90027-134 



airplanes. The hypersonic airplanes are likely to be very expensive because of both the technology re- 
quired and the small number of units needed (less than 300). Operating costs are also likely to be high. 
In addition, six dedicated ground facilities would have to be built, the cost of which must be included 
in the economic evaluation of the total transportation system. 

Design Requirements 

The study airplanes were designed to a set of requirements that included payload at 247 passengers; 
range of 5,000 nmi with a growth objective of 6,500 nmi, a maximum takeoff field length of 12,000 feet 
at sea level 86 °F, and a maximum approach speed of 160 keas at maximum landing weight. 



15 



10 - 



Hours 



High speed flight 

Transfer, 30 min at each end 



All-subsonic 
system 
(Mach 0.84) 



All-supersonic 
system 
(Mach 3.2) 




Superhub 
system 



10 15 20 

Dedicated design Mach number 

Figure 12. Average Trip Time -Superhub System 



5-U90027R1-135 



ENVIRONMENTAL CONCERNS 

Environmental acceptability is a key element of any HSCT program. If not properly accounted 
for in the HSCT design, environmental limitations could substantially reduce use of the vehicle and, 
in the most extreme circumstance, prohibit vehicle operation altogether. The primary areas of environ- 
mental impact identified by this study were engine emissions effects, community noise, and sonic 
boom. 

A viable HSCT must be designed so that its engine emissions have no significant impact on the 
Earth's ozone layer. This is based on the justifiable public concern about the impact of long-term de- 
pletion of the Earth's protective ozone layer. 

Operation out of conventional airports was determined to be a requirement for achieving adequate 
HSCT utilization. Accordingly, a viable HSCT must produce noise levels no higher than its subsonic 
competition. Studies indicate that, with projected suppression technology, achievement of FAR36 
Stage 3 noise levels may be possible. 

The sonic-boom overpressure level of a large, long-range HSCT designed for minimum weight is 
unacceptably high for overland flight in populated areas (overpressure of 2 to 3 Ib/f^). Commercial 
overland supersonic flights are, therefore, not allowed by U.S. law. The airplanes under study have 
been evaluated with subsonic flight profiles over land, which results in an adverse economic and mar- 
ket impact. Thus, there is impetus to explore low-boom designs that allow some form of overland 
supersonic operation. 

VEHICLE DEVELOPMENT 

Initial Assessment 

The technical and industrial progress achieved in the last century has demonstrated that, given 
enough time, technical achievement is almost limitless. Thus, rational judgments on technical 
feasibility must be in reference to specific time scales. For HSCT development, two time periods were 
defined. The first timeframe was defined as the earliest date that an economically viable and environ- 
mentally safe HSCT could be produced. The certification date was judged to be the year 2000, and 
is consistent with projections of market needs in terms of international traffic growth and current sub- 
sonic fleet replacement. The second time period defined was the year 2015 when certain advanced 



10 



technologies would have matured, some of which could possibly be developed as part of the proposed 
National Aerospace Plane program. 

The initial assessment of vehicle technology was organized into studies for each of several bands 
of Mach number (table 2). These bands were defined either by differences in technology readiness 
dates or in classes of airframe and engine technology. 

Three engine manufacturers, Aerojet General, General Electric, and Pratt and Whitney, provided 
data for advanced, conceptual engines appropriate for a series of commercial transports with a cruise 
speed between Mach 2.4 and Mach 10.0. Turbomachinery cycles were used to power the lower Mach 
number vehicles. A combined turbomachinery-ramjet cycle was used at Mach 4.5, an air turboramjet 
at Mach 6.0, and a supersonic-combustion scramjet at Mach 10.0. Engine cycle thermodynamics and 
properties of the available engine materials influence the engine cycle choice for each flight Mach num- 
ber. The engine concepts are illustrated in figures 13 and 14. 

Mach 3.2 is near the projected upper limit of using wing-integral fuel tanks for cruise fuel. Mach 
3.2 operation will require extensive development of fuels with higher thermal stability and fuel tank 
designs with low thermal conductivity. Mach 4.0 is near the projected upper limit for conventional 
turbojet-fan engine cycles and for thermally stable jet fuel (TSJF) use. Mach 4.0 is also considered to 
be the upper limit for a year 2000 HSCT because of very high technology risks and formidable design 
complexities that would need to be addressed in this relatively short development time period. For 
the year 2015, the continued technology development programs would provide more efficient configu- 
rations for Mach numbers up to Mach 4.0. In addition, the more advanced technology would open 
up design options for even higher Mach numbers. 

Above Mach 4.0 it is projected that cryogenic or endothermic fuels would be required to satisfy 
heat sink demands. Mach 6.0 is near the upper projected limit for liquid methane, endothermic fuels, 
and the ramjet as the cruise propulsion system. Mach 8.0 is near the projected upper limit for uncooled 
structural materials. At Mach numbers below this limit, however, areas such as the wing leading edges 
or nacelle inlets may require localized active cooling. At Mach numbers above 8.0, active cooling of 
structural materials is projected. Vehicle concepts for Mach numbers of 6.0 or greater were designed 
for dedicated superhub operations because the design compromise for achieving both high-speed and 
low-speed performance would have been prohibitive. 

Initial vehicle development evaluated 21 configuration concepts designed for Mach numbers be- 
tween 2.4 and 10.0. A screening process was used to evaluate the concepts on the basis of risk versus 
benefit. Of the 21 configurations, 6 were chosen for further development (figs. 15 through 20). Based 
on the following trends and study results, further work was concentrated on the lower range of Mach 
numbers: 

a. Aircraft size and design complexity increase significantly with increasing design Mach number. 

b. The airplane maximum takeoff weight is very sensitive to projected technology improvements for 
the higher Mach numbers. 



Table 2. Design Mach Number Selections 



Region 


Mach range 


Year of certification 


Limitation 


1 
2 

3 

4 
5 


2.0 to 3.2 
3.2 to 4.0 

4.0 to 6.0 

6.0 to 8.0 
8.0 to 25.0 


2000 
2000 

2015 

2015 
2015 


Thermally stable Jet fuel In wing tank 

Thermally stable Jet fuel 

Turbofan/turbojet 

Endothermic fuel 

Liquid CH4 

Ramjet 

Uncooled structural materials 








4-U90027-138 



11 



Forward 
variable area 
bypass injector 



Takeoff mode 



Aft variable area bypass Inlector 




Split fan 



Coannular acoustic plug nozzle- 
Supersonic Cruise Mode 
(a) GE Mach 3.2 Variable Cycie Engine 



Supersonic Cruise Mode 




Variable flap 



Crossover duct- 

Takceoff Mode 
(b) P&W Turbine-Bypass Engine Witfi NACA Nozzie 




SXXi 



Afterburner 



Nozzie 




(c) P&W Afterburning Turbojet 



Figure 13. Conventional-Fueled Engine Concepts 



5-U90027R2-136 



12 



Intake guide vanes (open) Variable nozzle 




Low Mach number 




■ Intake guide vanes (shut) Variable nozzle 



^m'. 



s^^^ 




High Mach number 



(a) GE Mach 4.5 Tandem Turbo Ramjet 




Compressor 



-Turbine 



Variable area nozzle 



— ( jmmi^ 



Turbine manifold - 

Fuel-rich 
mixture 
to turbine 




Combuster 




Pump 
(b) Aerojet Mach 6.0 General Air Turbo-Ramjet 




Turbojet mode 
Take off, climb, and accelerate to transonic speeds 



•'~*.^^_--' 1 




Turtx)jet-ramjet mode 
Transonic to supersonic speeds: climb and accelerate 




Ramjet/scramjet mode 
Supersonic climb, acceleration, and cruise 

(c) P&W Mach 10.0 Turbo-Ramjet-Scramjet 



Figure 14. Cryogenically Fueled Engine Concepts 



5-U90027R2-137 



13 



ECONOMIC EVALUATION 



The concept of life cycle operating costs has been developed to satisfy the need for an economic 
companson method that accounts for the actual cash direct and indirect costs incurred^" operatTn^ 
an airplane as well as mcluding all "ownership costs." Cost elements identified include the Mow ng 

a. Cash direct cost elements, which include- luiiuwing. 

1. Flight crew costs. 

2. Fuel burned. 

3. Airframe maintenance. 

4. Engine maintenance. 

5. Hull insurance. 

b. Indirect costs, which include— 

^' tXmlnf^ ^''''"'"^' ^"'""^' ^•^'^'■^f^-ha^dling. maintenance, and ground handling 

c. LL'rlTp ^o'tt'"'^ ^^'^^' P^^^^"g^^-h^"d""8' ^g^"<=y commissions, passenger insurance). 

econ^mi^vTaS orHsTr'^n'H"''' ? ^'""I"' '^''^'"^^ "'^ ^^^^'^ °P^^^^'"g '^'' ^o evaluate the 
economic viability of HSCT study configurations. This economic horizon is a trendline relationshio 
of life cycle operatmg costs and airplane size. It was based on projected advanced derivat^I of 1^^ 
Boeing 767 and 747 aircraft and allows comparisons of a wide variety of passenger sLt counts TO^ 
economic model was used in all phases of the contract to define market value omfcT desifins^nd 

IsSeT"'" '''''"" ^'^'"^"'"^"^"^"^"^^^^^^^ 

Ek;onomic Viability 

uJl ^' ,7"°'"*'^^ "y ^'^•'•^'/he HSCT must provide a reasonable financial return for both the air- 
m^Kt h. 1 "J^^^^f^^^"^^^,^- ^y •"^'■^^^^d operating and ownership costs associated with an HSCT 
must be largely overcome by increased productivity due to speed. The sale price must a low an ade 
quate return on investment and still elicit enough demand for Ihe HSCT to justify thetrgeir^estoem 
in development and production costs. To the extent that increased costs cannm be SZe bv in 
creased productivity, higher ticket prices must be charged, thereby reducing the markefSdim^na^ 
estimates have been made of the response of the projected HSCT market fo iLTeases in pri^ '^ 
th.t '""K^",' of technology based on this evaluation, is illustrated in figure 32. TOs evaluatfoiThows 
that presem day technology is not adequate to allow the necessary profit margin rMachT4 HS^^ 
designed with today's technology would require a 50% to 60% increase in average ticket price oS 
contemporary subsonic transports. This would reduce demand to the point that fhe tota worid^de 
fleet requirement is estimated to be 300 units or less, an inadequate number to support a vTable pro- 
gram. However, with technology available for year 2000-certified airplanes, the requ^ed revenues a^e 
ower, primarily because of the smaller vehicle required to perform the design mSn ^e resuU s 
that a ticket price increase of 18% would be required and the fleet reauirement won IHh! 

rnrarbrsi'^^rwouM""^^^^^^ 

increase by 8%. This would result in a fleet requirement of 950 to 1 050 units 

The impact of design Mach number on the market captured by the HSCT is shown in figure 33 
Assuming year 2m certification, increasing design speed from Mach 2.4 to Mach 2 sToists fhe fare 
ZT XTZ^^" ^f '"'"'^"f '^' '^^'^'' '^^'""''^ ^° 30%, requiring a fleet size oMO^o 5M unks 
1^-^rtll ri!" '^S!ir.?.f; ^^y}^' -'^--'^ to -n the Required return on nvStm'm 



Variable 
Intake 



Intake guide vanes (open) Variable nozzle 




Low Mach number 

Variable 
Intake 



Intake guide vanes (shut) Variable nozzle 




High Mach number 



(a) GE Mach 4.5 Tandem Turbo Ramjet 




Compressor 



-Turbine 



Variable area nozzle 



/ juuiuiliiS 



Turbine manifold - 

Fuel-rich 
mixture 
to turbine 




Combuster 




Pump 



(b) Aerojet Mach 6.0 General Air Turbo-Ramjet 




TurtDojet mode 
Take off, climb, and accelerate to transonic speeds 




Turbojet-ramjet mode 
Transonic to supersonic speeds: climb and accelerate 





^^^sfcCJ^ yy "v, i'v!!! » — "r^^ ^ 



■ »^.:?*;;J< 



Ramjet/scramjet mode 
Supersonic climb, acceleration, and cruise 

(c) P&W Mach 10.0 Turbo-Ramjet-Scramjet 



Figure 14. Cryogenically Fueled Engine Concepts 



5-U9CK)27R2-137 



13 




Figure 15. Mach 2.4 Configuration 



4-U80027-139 



Scale, ft 

25 50 




Figure 16. Mach 3.2 Configuration 



4-U90027-140 



c. 



Average block time decreases slowly as design cruise speed increases above a Mach number of 3.0, 
suggesting economic gains will not increase proportionally with design cruise Mach number, 
d. Significant technology and design advances are required for an efficient long-range HSCT, even at 
lower supersonic cruise Mach numbers. 



Final Assessment 

During the final study phase, new configurations were developed at Mach 2.4, 2.8, and 3.2. Evalua- 
tion of these configurations indicated that the lowest maximum takeoff weight, operating-empty 
weight, and block fuel occurred at Mach 2.4. Even though the minimum block time occurred with the 



14 




Figure 17. Mach 3.8 Configuration 



4-U90027-141 




Figure 18. Mach 4.5 Configuration 

4-U90027-142 

Mach 3.2 configuration, maximum economic potential occurs at Mach 2.4. This occurred because im- 
proved utilization due to reduced flight times was not enough to offset the increased cost of a heavier 
Mach 3.2 configuration. Technical risk evaluation in conjunction with this configuration assessment 
was reason to focus the environmental impact studies at the lower Mach numbers. The Mach 2.4 
baseline airplane is shown in figure 21. This airplane has a maximum takeoff weight of 745,000 lb, a 
wing area of 7,466 ft^, and an engine airflow of 582 Ib/s. 



15 



Scale, ft 

25 50 100 



I." 
i: 




U;=; 



p — ■■tin 



ciz: 



10 




iHZL 



c:!!r 



1=IUJ 



"•: ^r^il 




Figure 19. Mach 6.0 Configuration 



4-U90027-143 



Scale, ft 

25 50 



100 



,, tu-^ 




wm JL iM 








F/gare 20. Mach 10.0 Configuration 



4-U90027-144 



16 



Scale ft 




Figure 21. Mach 2.4 Baseline Configuration 



4-U90027-145 



REQUIRED TECHNOLOGIES 

Advanced Jet Noise Reduction Concepts 

Jet noise can be diminished either by reducing the jet velocity or through nozzle noise-suppressor 
technology. The jet noise reduction concepts considered in this study are illustrated in figure 22. Partic- 
ular attention was given to a naturally aspirated, coannular (NACA) nozzle concept. The NACA nozzle 
is a high-radius-ratio plug nozzle system incorporating a crossover duct, which allows ambient (sec- 
ondary) air to cross inside the primary stream and be aspirated through the inner annulus of the coan- 
nular nozzle. The aspirated ambient flow is intended to provide rapid mixing on the inner boundary 
of the outer annulus primary stream to reduce the jet noise. The NACA nozzle has been shown to 
provide significant aspiration of free stream air with small performance penalties at takeoff 
conditions. Consequently, it is believed that the NACA nozzle offers good potential for jet noise reduc- 
tion with small thrust penalties. However, this concept would require considerable development to 
confirm its performance and qualify it for use on a commercial airplane. 

Emission Reduction Concepts 

Achieving the goal of having no significant effect on the ozone layer may require the reduction of 
oxides of nitrogen (NOx) engine emissions. The engine manufacturers conducted studies of derated 
engine cycles and high-risk, low-emission combustor concepts. The concepts considered most promis- 
ing were the staged-lean combustor; rich-burn, quick-quench combustor; and lean, premixed and pre- 
vaporized combustor. These concepts could potentially reduce emissions in a range from three-fourths 
to one-sixth of the untreated level, but would require an aggressive research and development effort. 



17 




Pneumatic 
oscillators 




Acoustic Lining 



Suppressor 










y 




V2 














Inverted Velocity Profile 



Ejector 




Observer 



Shield stream (high 
temperature, low velocity) 



Supersonic cruise mode 




Crossover duct 



■ Variable flap 
Takeoff mode 



Thermal Acoustic Shield Turbine-Bypass Engine With NACA Nozzle 

Figure 22. Jet Noise Reduction Concepts 



5-U90027R2-148 



18 



Fuel Technology 

The fuel technology study identified and evaluated production, cost, property, and other nonair- 
craft system-related factors that would affect the use of both conventional and unconventional fuels 
in HSCTs. The fuels study included modified conventional, endothermic, cryogenic, and other fuels 
such as slushes and gels. The study emphasized— 

a. The availability and cost associated with modified conventional fuels (thermally stable jet fuels). 

b. Liquid methane costs (liquid methane is assumed to be the same as purified liquefied natural gas). 

c. On-airport costs for both conventional fuels and liquid methane. 

Aerodynamics 

The aerodynamic design of each of the study configurations included optimized camber/twist dis- 
tributions and area-ruled fuselages. The wing spanwise thickness distributions and airfoil shapes were 
constrained by structural depth requirements. The nacelles were shaped and located aft under the 
wing to develop favorable aerodynamic interference subject to ground clearance, engine geometry con- 
straints, and structural design considerations. 

High-speed aerodynamic characteristics for all of the concepts were developed using the methods 
from earlier NASA studies. Projections for year 2000 technology improvements have been included 
in the drag build-ups. These projections include skin friction drag reduction resulting from the use 
of an outer surface treatment such as riblets over 90% of the vehicle wetted area; reduction in volume 
wave drag and drag-due-to-lift resulting from design methodology improvements; and incorporating 
an improvement in the wind tunnel to flight test drag correlation. 

The drag breakdown for the baseline airplane is shown in figure 23 and lift/drag versus Mach num- 
ber is illustrated in figure 24. 

The high lift system is designed to increase wing lift for liftoff and touchdown. It must be designed 
to minimize drag during climbout and approach to reduce airport noise levels. In general, the lead- 
ing-edge and trailing-edge flaps are simple hinged surfaces. Low-speed performance is improved by 
repositioning the flaps relative to the conventional low-drag position for higher lift. For liftoff and 
touchdown, leading edge flaps were raised to increase vortex lift. After liftoff, the flaps were positioned 
for minimum drag. 



100 



Total 

cruise 

drag,~% 



50 



Drag due to lift 



Friction 




Volume wave 




Figure 23. Drag Breakdown— Mach 2.4 Basel ne 



4-U90027-147 

19 



Lift/drag 12 — 




1.2 1.6 

Mach number 
Figure 24. Lift /Drag Versus Mach—Macli 2.4 Baseline 



2.0 



2.4 



4-U90027-148 



Stability and Control 

The primary task for stability and control has been the estimation of horizontal and vertical tail 
size and center-of-gravity limits that satisfy critical stability and control criteria. HSCT configurations 
are designed using a control-configured vehicle design approach that employs the flight control system 
to stabilize as well as control the airplane, which results in a more efficient aerodynamic and structural 
configuration. The required stability augmentation system must be of sufficient capability and reliabil- 
ity to provide acceptable handling qualities over the operational flight envelope up to the maximum 
useful angle-of-attack. The flight control system will be used to limit or prevent excursions outside this 
envelope. 

Structures and Materials 

Candidate structural materials were selected by (1) surveying published research, material suppli- 
ers, and aerospace contractors to identify commercial or developmental materials with potential appli- 
cability; (2) estimating mechanical properties based on available published data and developmental 
goals; and (3) forecasting availability by assessing progress in development versus goals, determining 
technical complexity in achieving these goals, and estimating process scaling necessary to support a 
large production program. A significant development effort to ensure availability of technology was 
assumed. Potential materials, maximum use temperatures, and predicted availability are summarized 
in figure 25. 

20 



Polymer matrix composites 

• Epoxy 

• Polyetheretherketone 

• Toughened BMI 

• Thermoplastic polylmlde 

• Polylmlde 

• Fluorlnated polylmlde 



Legend: 

I I Year 2000 availability 

IMWI Year 2015 availability 



Metals 

• Aluminum 

• Aluminum lithium 

• RS aluminum 

• Titanium 

• RS titanium 

• Intermetalllce 




Metal matrix composites 

• Aluminum matrix 

• Titanium matrix 

• Intermetalllo matrix 




300 



1,800 



600 900 1,200 1,500 

Temperature range, °F 
Figure 25. Structural Material Candidates and Projected Temperature Range for HSCT Application 



6-U90027R3-149 



The structural materials for Mach 2.8 and below judged to have the most potential and to be avail- 
able for year 2000 certification were identified. These materials were high-temperature thermoplastics 
or toughened thermosetting polyimide composites. Ingot titanium alloys were selected for the higher 
Mach numbers. Even though they have the most potential for a lightweight, cost-effective HSCT, poly- 
meric composite systems for high-temperature service have inadequate processibility and unproven 
long-term, thermal and environmental resistance for application in a commercial program. 

Significant development is required to optimize these materials, develop automated processing 
methods, and evaluate their long-term performance in the severe HSCT environment. 

By the year 2015, it is projected that the maturation of metal matrix composite and rapid solidifica- 
tion technology will make them available for application on the HSCT. Current material forms, pro- 
cesses, and production equipment available in the industry are not adequate to produce the large 
structure required for an HSCT program. Development is necessary to scale processes and evaluate 
long-term, high-temperature performance of these materials. 

Support materials compatible with the selected structural materials are required for a viable com- 
mercial program. Support materials include adhesives, seals and sealants, finishes, and lightning pro- 
tection materials. Generally, support materials are available with thermal stability applicable to a 
cruise speed of Mach 2.8 or below. The performance and long-term durability of current support mate- 
rials are necessary for their application to the HSCT Development of improved temperature resistant 
materials is required for high Mach number configurations. 

Structural weights for performance calculations are based on the structural concepts, arrange- 
ments, and procedures used in the study reported in "Study of Structural Design Concepts for an Ar- 
row Wing Supersonic Transport Configuration" (ref. 2). A number of potential materials were selected 
for years 2000 and 2015 as described previously. Based on the projected mechanical properties of these 
materials, panels taken from ten locations on the fuselage and six locations on the wing were redesigned 
and resized for strength, making allowance for the change in operating temperature at the higher Mach 
numbers. These locations were selected to represent the range of typical design load conditions on 
the airframe structure. Based on the weights of these structural elements, the weight of the airframe 
for each airplane configuration was estimated for use in the performance calculations. 



21 



Weight and Balance 

The weights databases of the Boeing 2707-300 (U.S. S.S.T.) and other studies have been used for 
baseline structural sizing, loads, systems and equipment definition, design criteria, and payload sys- 
tem definition. Passenger comfort level requirements according to the current Boeing and airline com- 
panies' definition were substituted for the definition used in the model 2707-300. Advanced technology 
materials were apphed for concepts projected to be certified in years 2000 and 2015. 

Impact of Improved Technology 

Advanced technology is essential to achieve the desired range capability (5,000 nmi) within a realis- 
tic size limit (maximum takeoff weight of 900,000 lb). Figures 26 and 27 show the impact of technology 
advances projected for year 2000 certification versus that currently available for year 1995 certification. 
These data show that, collectively, advanced technology reduces the maximum takeoff weight from 
1 million pounds to 745,000 lb (about 25%), with advanced structures and materials providing the larg- 
est single benefit. The figures also show the same data plus the impact of further technology 



Legend: 

Titanium - - - • 
Composite — _ — 

1,800 



1,600 



Maximum 
takeoff 
weight, 
lb X 1,000 



1,400 



1,200 



1,000 



800 



600 



400 




Concorde 
technology, 
year 1971 
certification 



Present 



jr technology, 
\ year 1995 



year 
certification 



r Projected 
technology , 
year 2000 
certification 



Maximum 
weight 



Projected 
technology, 
year 2015 
certification 



Chicago 



' Paris to * New York ^ Francisco Los Angeies New York San f^rancisco 

New York to Rome •* to Tokyo to Tokyo to Tokyo to Hong Kong 



M.^1,1 



± 



1 A 



3,000 



4,000 



5,000 



6,000 



Range, nmi 
Figure 26. Impact of Technology— Mach 2.4 Baseline 



5-U90027H4-150 



22 



1,100 



1 ,000 — 



900 



Maximum 
takeoff 
weight , 
lb X 1 ,000 



800 



700 



600 



500 





Propulsion 



Year 2000 
projections 



Composite 
materials 




Year 2015 
projections 



Aerodynamics systems 



Composite 
materials 



Figure 27. 



Impact of Technology— Mach 2.4, 247-Seat Airplane With Year 2000 Certification, 
5,000-nml Design Range 



S-U90027R2-151 



improvements projected for year 2015 certification. The required maximum takeoff weight is reduced 
from 745,000 lb to about 585,000 lb (about 20%), with advances in propulsion technology providing 
the largest single benefit. A year 2000-certification airplane could conceivably use this technology im- 
provement for the range growth strategy of the HSCT family concept (fig. 28). 

ENVIRONMENTAL EVALUATION 

Upper-Atmosphere Emissions/Ozone Impact 

The study provided NASA with emissions data for representative fleets of airplanes for analyses 
with math models of the Earth's atmosphere. The impact on the airplane size of using reduced emis- 
sion engine combustion technology was studied. 

Studies to assess the effect on vehicle design of incorporating reduced-emission engines indicated 
that significant reduction in NOx emissions can be obtained with a resultant 2.2% to 3.7% increase 
in maximum takeoff weight. Of the concepts considered, the lean, premixed and prevaporized combus- 
tor has the greatest potential for NOx reduction (approximately one-sixth the base level), but carries 
the highest technical risk. The staged-lean combustor provides less NOx reduction (approximately 
three-fourths the base level) with what is considered a low technical challenge. The rich-burn, 
quick-quench combustor may prove acceptable with a significant NOx reduction (approximately 
one-fourth the base level) with a smaller maximum takeoff weight increase than either the lean, 
premixed and prevaporized or the staged-lean combustor and is considered to have a lower 
development risk. 



23 



7,000 



6,000 



Range, 
nml 



5,000 



4,000 



3,000 



Los Angeles to Sydney 



New York to Tokyo 



1 200 passengers, 
advanced engines 




• 250 passengers, 
improved engines 



Los Angeles 
to Tokyo 
(Honolulu to Sydney 



New/ York to Rome 



New York to Paris 



^L Initial delivery, 
•^ 250 passengers 



X 



) Increased payload 
with improved and 
advanced engines 



> 300 to 350 
passengers, 
Improved 
engines 



• 350 to 400 
passengers, 
advanced 
engines 



1995 



2000 



2005 
Year 



2015 



Figure 28. HSCT Growth Strategy 



3-U90027-152 



Community Noise 

Two different goals were pursued in two parallel studies of community noise and the HSCT The 
first was to achieve compliance with FAR36 Stage 3 noise limits; the second was to produce the same 
overall effect on the community as a Boeing 747-200 airplane configuration, which just meets the 
Stage 3 criteria. The baseline configuration used very aggressive jet noise suppression technology to 
reduce takeoff noise levels. In addition, vehicle configurations that had oversized engines and/or wings 
were studied to evaluate the effects of these changes on the community noise levels, airplane weight, 
and economics. Oversizing the wing was not beneficial. Increasing engine size in conjunction with ad- 
vanced, automatic thrust modulation reduced takeoff noise to subsonic Stage 3 requirements, but also 
incurred a 4.7% increase in takeoff gross weight and a significant degradation in economic potential. 

In the airport study, residential noise exposure was evaluated at 18 airports; the assessments were 
made with 85 dBA noise contours (footprints). TWo HSCT footprints were compared with the Boeing 
747 footprint as shown in figure 29. The residential area exposure at levels greater than 85 dBA was 
nearly the same for the HSCT with a 20% programmed lapse rate procedure as the Boeing-747 (actu- 
ally 6.5% less because the HSCT footprint is slightly shorter). If sideline noise requirements were 
somewhat reduced or trade provisions increased, maximum thrust could be used for takeoff. The use 
of maximum takeoff thrust was found to expose 43.2% less residential area based on an average of 
18 airports. It was found that, at most airports, larger residential communities are downrange of the 
runway and the shorter footprint more than makes up for the increased width. A supersonic Stage 3 



24 




8 

D 







Q 


§ 




CM 


o> 




1^ 


to 




1^ 

2 


o 




o 


o 




to 


o 


C 


1 


CO 
CO 


tt> 


o 




It 


c 
o 




0> 


y> 


s 




p. 


o 




t 


r-T 




o 


CM 


t 
o 


O 

1 






< 




o 

c 


OQ 




O 


O 


(0 


oo 




n 










CM 




(0 

o 

c 
o 


o 
o 




O 


o 




<& 


m 




CO 






1 

O) 
CM 


o 




<t> 


o 




^ 


o> 




ii: 



to Tj i: 



25 



noise rule that takes into account the HSCT's unique ability to climb away from the community has 
the dual benefit of reducing the impact on the community and improving the economics of the airplane. 

Sonic Boom 

All vehicles in the viability studies were configured to fly supersonically over water and subson- 
ically over land. However, because of the significant impact of supersonic overland flight on fleet eco- 
nomics, a configuration was evaluated that was designed to reduce the level of sonic boom at Mach 
1.5 to a potentially acceptable level. This design would potentially be capable of cruising over land 
at supersonic speeds, increasing utilization and reducing flight times. 

This study examined several options for reducing the sonic boom shock wave amplitude to a target 
overpressure of 1.0 Ib/ft^. This level, with a typical rise time of 6 ms, corresponds to a potentially ac- 
ceptable level of 72 dBA for restricted overland flight (corridors). Acceptability is based on previously 
published human response testing (ref. 3). 

The configuration studies focused on a Mach 1.5 overland design because the concept allowed a 
more reasonable fuselage length and required only minimum changes to an arrow wing. The resulting 
airplane is shown in figure 30. Compared to the Mach 2.4 baseline, the forebody was lengthened by 
10 ft and widened slightly, a wing strake was added, nacelles were staggered, and an arrow planform 
was used for both the wing and horizontal tail. The maximum takeoff weight for this low-boom configu- 
ration is approximately 3% greater than the baseline aircraft. 

The initial attempt at achieving a low-boom profile was only partially successful. In particular, the 
inexact design methods resulted in undesirable intermediate shocks and a strong tail shock. Because 
the human auditory system is sensitive to shock waves, only a small reduction was obtained. Pressure 
signature and resulting loudness predictions at Mach 1.5 are shown in figure 31. More detailed 
configuration design studies are required to reach the target of 72 dBA. 




Figure 30. Low-Sonic-Boom Configuration 



5-U90027R 1-154 



26 



Baseline at Mach 2.4 



Target 



2—1 



1 — 



Overpressure, 
Ib/ft2 



-1 — 



-2 — ' 



Low-sonlc-boom 
configuration 




500 
~1 



X = ft 



Pressure Waves at Ground 



Calculated 
loudness, dBA 



85—1 



80 — 



75 — 



70 



65— ' 



Target ■ 




Baseline at Mach 2.4 



Low-sonlc-boom 
configuration 



Real atmosphere 
typical variation 



1 \ 

2 4 6 8 10 12 14 

Shock wave rise time, msec 
Resulting Loudness 



Figure 31. Mach 1.5 Pressure Signature and Loudness Predictions 



4-U90027H1-155 



27 



ECONOMIC EVALUATION 

The concept of life cycle operating costs has been developed to satisfy the need for an economic 
comparison method that accounts for the actual cash direct and indirect costs incurred in operating 
an airplane as well as including all "ownership costs." Cost elements identified include the following- 

a. Cash direct cost elements, which include— 

1. Flight crew costs. 

2. Fuel burned. 

3. Airframe maintenance. 

4. Engine maintenance. 

5. Hull insurance. 

b. Indirect costs, which include— 

1. Airplane-related (cleaning, fueling, aircraft-handling, maintenance, and ground handling 
equipment). 

2. Passenger-related (food, passenger-handling, agency commissions, passenger insurance) 

c. Ownership costs. 

An "economic horizon" was used to provide a reference life cycle operating cost to evaluate the 
economic viability of HSCT study configurations. This economic horizon is a trendline relationship 
of life cycle operating costs and airplane size. It was based on projected advanced derivatives of the 
Boeing 767 and 747 aircraft and allows comparisons of a wide variety of passenger seat counts This 
economic model was used in all phases of the contract to define market value of HSCT designs and 
the revenue required to obtain the desired return on investment for those designs for which prices were 
estimated. 

Ek;onomic Viability 

To be economically viable, the HSCT must provide a reasonable financial return for both the air- 
lines and the manufacturers. Any increased operating and ownership costs associated with an HSCT 
must be largely overcome by increased productivity due to speed. The sale price must allow an ade- 
quate return on investment and still elicit enough demand for the HSCT to justify the large investment 
in development and production costs. To the extent that increased costs cannot be overcome by in- 
creased productivity, higher ticket prices must be charged, thereby reducing the market. Preliminary 
estimates have been made of the response of the projected HSCT market to increases in price 

The impact of technology, based on this evaluation, is illustrated in figure 32. This evaluation shows 
that present day technology is not adequate to allow the necessary profit margin A Mach 2 4 HSCT 
designed with today's technology would require a 50% to 60% increase in average ticket price over 
contemporary subsonic transports. This would reduce demand to the point that the total worldwide 
fleet requirement is estimated to be 300 units or less, an inadequate number to support a viable pro- 
gram. However, with technology available for year 2000-certified airplanes, the required revenues are 
lower, primarily because of the smaller vehicle required to perform the design mission. The result is 
that a ticket price increase of 18% would be required and the fleet requirement would be 
approximately 650 to 750 units. If year 2015-certification technology was used, ticket price would only 
increase by 8%. This would result in a fleet requirement of 950 to 1,050 units. 

The impact of design Mach number on the market captured by the HSCT is shown in figure 33 
Assuming year 2000 certification, increasing design speed from Mach 2.4 to Mach 2 8 boosts the fare 
increase to over 25% and reduces the market captured to 30%, requiring a fleet size of 400 to 500 units 
Ihe Mach 3.2 design does not close, as the yield required to earn the required return on investment 
is rising more steeply than the yield available. 

The key assumption behind the economic closure trends shown in figures 32 and 33 is the trade 
of market share against ticket price for a 50% time savings. If the decline in market share with higher 
ticket price is steeper, then the "yield available" cuive of figures 32 and 33 may have lower slope with 
2o 



Average 

yield, 

C/revenue 

passenger 

miles 



20 



18 — 



16 — 



14 — 



12 



10 



Yield 
available 



Subsonic 

fleet 

yields 



250 to 350 
units 
I 



• 65% load factor 

• Based on 50% time savings 



Today's technology 



Yield 
required 
for 12% 
return on 
Investment 




650 to 750 
units 

I 



950 to 1.050 

units 

I 



100 



" 25 50 75 

Mari<et captured by HSCT, % 
Figure 32. Economic Viability— Technology Impact on Fleet Size Based on Mach 2.4, 247-Seat 
Design With 5,000-nml Range 



5-U90027R2-156 



20 



18 



16 

Average 
yield, 

0/revenue 14 
passenger 
miles 

12 



10 



• 65% load factor 

• Based on 50% time savings 



Yield 
available 



IVIach 3.2 



Yield required 
for 12% return 
on investment 



Subsonic 

fleet 

yields 




400 to 500 
units 



650 to 750 
units 



1 



100 



25 50 75 

Market captured by HSCT, % 
Figure 33. Economic Viability— Impact of Speed Based on 247-Seat Design With 5,000-nml Range 



5-U90027R2-157 



29 



decreasing market share. This would move the closure point to even lower values of marker share and 
sales base. 

While there is considerable uncertainty in the technical projections and the economic analyses of 
all such studies, results indicate the Mach 2.0 to 2.5 vehicles have maximum potential for economic 
viability. Compared to transports with greater cruise speeds, they maximize fleet size and meet the 
market needs for year 20(X) to 2005 introduction. Additionally, they represent reduced development 
investment and risk because of reduced size, complexity, and costs. 

CONCLUSIONS 

Market and Competition 

The market results show that a viable HSCT could acquire a significant portion of the growing, 
long-range, worldwide market. However, to achieve this result, the airplane must have the following 
characteristics: 

a. Environmentally acceptable (no special operating limits other than subsonic flight over land). 

b. Adaptable to the year 2000 airport system (i.e., no superhubs for the HSCT alone). 

c. From about 250 to 300 seats (in triclass seatings). Final seat definition is a function of productivity, 
which depends on Mach number and design range capabilities. 

d. A range of 5,000 nmi initially with growth to over 6,000 nmi. This increase will occur through weight 
growth; the use of improved engines; minimizing intermediate stops, which increase airline costs 
and passenger trip times; and allowing maximum flexibility of the airplane within an airline's sys- 
tem. Maximum flexibility will be reached only if the HSCT is used on routes suited to its capabili- 
ties, rather than as a direct substitute for 747 missions. 

e. Economically competitive with a year 2000 subsonic fleet (i.e., increases in utilization must over- 
come increased operating and ownership costs). 

f. Cruise Mach number should be consistent with minimum operating costs and maximum produc- 
tivity when considering design range tradeoffs. 

An HSCT with these characteristics could justify a total fleet size of over 1,200 aircraft between 
the years 2000 and 2015, serving primarily the long-range (2,500 nmi and greater), high-density market. 

Environmental Concerns 

The primary areas of environmental impact identified by this study were— 

a. Engine emission. Projections of advanced low-emissions burner technology indicate that an NOx 
emissions reduction from 30 + lb to approximately 5 lb of nitrous oxide emissions per 1,000 lb of 
fuel burned is possible. A clearer understanding of the effect of engine emissions on the atmo- 
sphere is being investigated using the best atmospheric models available and data from the current 
HSCT studies. This knowledge is essential to understanding the design requirements for an envi- 
ronmentally acceptable HSCT 

b. Community noise. The study shows that with projected suppression technology, achievement of 
FAR36 Stage 3 noise levels may be possible. The primary issues involved in achieving Stage 3 levels 
are— 

1. Development of projected jet-noise suppressor technology. 

2. Possible modifications to the Stage 3 rules. The unique characteristics of an HSCT could justify 
a different trade between sideline noise and takeoff noise, which could further reduce noise to 
the majority of the community. Requirements could also focus on the area exposed to a given 
sound level to take into account the operating characteristics of an advanced HSCT in reducing 
residential area exposed to noise. 



30 



c. Sonic boom. Subsonic, boomless overland flight was assumed for the basic technical and economic 
viability estimates. However, a preliminary low-sonic-boom-design study suggests that a combina- 
tion of fuselage shaping, wing planform choice, and a cruise at reduced supersonic Mach has poten- 
tial for reducing boom overpressure levels. Acceptable sonic boom levels have not been 
established. Therefore, committing a design to a reduced sonic boom level is premature at this early 
stage. Continued effort must be made toward developing a low-boom configuration. 

Technical Feasibility 

Within the Mach 2.0 to 3.2 speed range, vehicles can be operated with kerosene-based fuels, engine 
cycles using conventional turbomachinery, an uncooled high-temperature composite, or a titanium 
primary structure. These vehicles would be capable of operating from existing airports. 

Based on the results of the contract studies and other independent studies focusing on lower cruise 
speed vehicles, maximum potential for an environmentally sound, technically feasible HSCT exists for 
a vehicle designed to cruise at Mach 2.0 to Mach 2.5 over water and Mach 0.9 over land. 

Economic Viability 

Preliminary estimates of the response of the projected HSCT market to increases in ticket cost 
have been measured against the revenues needed for the airplanes studied in this and other indepen- 
dent studies to provide adequate profit margins to the manufacturer and the airlines. Based on this 
evaluation, the following conclusions can be drawn: 

a. Present technology is not adequate. 

b. A year 2000, Mach 2.0 to 2.5 HSCT shows promise (potential total market of 650 to 750 airplanes). 
While this would be an adequate demand for a single manufacturer, it is not an adequate market 
for two or more. 

c. A Mach 2.0 to 2.5 HSCT with the advanced technology projected to be available for a year 2015 
airplane (either as an all-new airplane or an advanced derivative of a year 2000 airplane) is more 
encouraging. With this technology, the potential total market is estimated at 950 to 1,050 airplanes, 
which clearly represents a business opportunity for two manufacturers. 

d. Technology that reduces the weight and cost at Mach 2.0 to 2.5 has a much greater impact on eco- 
nomic viability than technology that enables higher cruise Mach numbers. 

Key areas of improvement that would directly impact economic performance are— 

a. Reduced structural weight. 

b. Improved engines available for year 2000 vehicles. 

c. Increased aerodynamic performance through improved wing planforms and hybrid laminar flow. 

Finally, while the development costs of vehicles in the preferred Mach range may be considerably 
higher than the costs of a similar-sized subsonic vehicle. Government support of the production pro- 
gram for an HSCT would not be required if such a vehicle were economically viable. 

RECOMMENDATIONS 

Technology Development Program 

Potential for a successful U.S. commercial high-speed transport exists for the year 2000 market 
if aggressive technology development is undertaken in the near term. It is recommended that a joint 
NASA-industry technology development and validation program be undertaken to address key tech- 
nology areas. This program would optimize the likelihood of achieving environmental acceptability 
for, and economic viability of, an HSCT cruising between Mach 2.0 and 3.0. The cost of this program 
would be a small fraction of the total development and production costs, but could be key to receiving 

31 



the commitment from airframe and engine manufacturers necessary to achieve the timely development 
and production of a successful HSCT and, ultimately, to ensure the HSCT's success in the worldwide 
marketplace. 

Technology Needs 

Many technology development needs are enabling, meaning that they are essential to achieve vi- 
ability, and others are high-leverage items that offer significant payoff in risk reduction or economics. 
The list of required and/or desirable technology developments covers virtually all technology areas 
and disciplines and must be prioritized. One basis for prioritization is the development of technology 
to demonstrate environmental acceptability, without which the HSCT program cannot be launched. 
(Examples of these technologies are low-emission burners and noise suppression technology.) Other 
factors that set priorities are the degree to which the technologies are time-critical, high-risk, or 
high-cost, or are potentially high in value in economic payoff. 

Based on maximum potential for environmental and economic viability, the highest near-term 
priorities for technology development are— 

a. Low-emissions technology. 

b. Noise-suppressor technology. 

c. Variable-cyle engine technology. 

d. High-temperature, durable-composite structures and materials. 

e. High-lift aerodynamics. 

f. High-temperature metals compatible with lightweight composite structures. 

These are all high-value, high-cost items that will make critical contributions to the environmental 
and economic factors and they are time-critical to the aircraft certification date of year 2000. Serious 
research and development of each of these items should be initiated by 1990. 

Technology development needs for longer term, higher risk vehicles have been identified. These 
are considered of secondary priority to the Mach 2.4, year 2000 vehicle, but could provide enhance- 
ments in economics and possibly speed. They are applicable to a later timeframe for certification. 
Those areas needing development include— 

a. Advanced engine concepts. 

b. Advanced vehicle concepts. 

c. Laminar flow control. 

d. Higher temperature materials for higher speed vehicles. 

e. High-thermal-stability fuels. 



32 



REFERENCES 

1. Boeing Commercial Airplanes, "Current Market Outlook," February 1988. 

2. "Study of Structural Design Concepts for an Arrow Wing Supersonic Transport Configuration," 
Volume 1, NASA CR- 132576-1, August 1976. 

3. Brown, J. G. and Haglund, G. T, "Sonic Boom Loudness Study and Airplane Configuration Devel- 
opment," AIAA Paper 88-4467, presented at the AIAA/AHS/ASEE Aircraft Design, Systems, and 
Operations Conference, September 7-9, 1988, Atlanta, Georgia. 



33 



(VIASA 



Report Documentation Page 



1. Report No. 

NASA CR-4234 



2. Government Accession No. 



4. Title and Subtltie 

High-Speed Civil Transport Study - 
Summary 



3. Recipient's Catalog No. 



5. Report Date 

September 1989 



6. Performing Organization Code 



7. Autlior(s) 

Boeing Commercial Airplanes 
New Airplane Development 



8. Performing Organization Report No. 



9. Performing Organization Name and Address 
Boeing Commercial Airplanes 
P.O. Box 3707 
Seattle, Wa 98124-2207 



10. Worit Unit No. 

505-69-01-01 



11. Contract or Grant No. 

NASl-18377 



12. Sponsoring Agency Name and Address 

NASA Langley Research Center 
Hampton, Va 23665-5225 



13. Type of Report and Period Covered 
Contractor Report 



14. Sponsoring Agency Code 



15. Supplementary Notes 

NASA Program Manager: 
Boeing Program Manager: 
Boeing Contract Manager: 
Final Report 



Charles E. K. Morris, Jr. 
Michael L Henderson 
Danella E. Hastings 



16. Abstract 

A system study of the potential for a high-speed commercial transport has addressed 
technology, economic, and environmental constraints. Market projections indicated a need for 
fleets of transports with supersonic or greater cruise speeds by the years 2000, to 2005. The 
associated design requirements called for a vehicle to carry 250 to 300 passengers over a range of 
5,000 to 6,500 nautical miles. The study was initially unconstrained in terms of vehicle 
characteristic, such as cruise speed, propulsion systems, fuels, or structural materials. Analyses 
led to a focus on the most promising vehicle concepts. These were concepts that used a kerosene- 
type fuel and cruised at Mach numbers between 2.0 to 3.2. Further systems study identified the 
impact of environmental constraints (for community noise, sonic boom, and engine emissions) on 
economic attractiveness and technological needs. 

Results showed that current technology cannot produce a viable high-speed civil transport; 
significant advances are required to reduce takeoff gross weight and allow for both economic 
attractiveness and environmental acceptability. Specific technological requirements have been 
identified to meet these needs. 



17. Key Words (Suggested by Author(s)) 

High-Speed Civil Transport Market 

Environment Economics 

Vehicle Development 



18. Distribution Statement 

Unclassified - Unlimited 
Subject Category 05 



19. Security Classlf. 
(of this report) 

Unclassified 



20. Security Classlf. 
(of this page) 

Unclassified 



21. No. of pages 

44 



22. Price 

A03 



.NASA-Langley. 1989 



For sale by the .National Technical Information Service, Springfield, Virginia 22161-2171